Preparation of high molecular weight alcohols



Patented Oct. 29, 1935 PREPARATION OF HIGH MOLECULAR WEIGHT v ALCOHOLSNorman D. Scott and Virgil L. Hansley, Niagara Falls, N. Y., assignorsto The E. I. du Pont de Nemours & Company, Incorporated, Wilmington,Del., a corporation of Delaware No Drawing. Application June 9, 1934,Serial No. 729,900

19 Claims.

This invention relates to the production of high molecular weightalcohols and more particularly to the reduction of esters of highmolecular weight fatty acids by reaction with alkali metal and a loweraliphatic alcohol.

The reduction of esters of high molecular weight acids to form the highmolecular weight alcohol by reacting the esters with alkali metal and alower aliphatic alcohol in a solution in the lower alcohol has long beenknown. The

method originally proposed (U. S. Patent 868,252) consisted in placingpieces of alkali metal in a closed container and slowly adding theretoan ethyl alcohol solution of the ester to be reduced. A large excess ofthe solvent alcohol and the alkali metal were used. After the reactionwas completed excess alkali metal and the alkali metal compounds weredecomposed by treating with alcohol and water and the higher alcoholformed was recovered by distillation. The reactions involved may berepresented as follows:

This method has not been adapted for economical commercial practicebecause of low yield of product and poor reduction efficiency, that is,a considerable portion of the alkali metal used is consumed with theevolution of hydrogen from the solvent alcohol rather than being used toreduce the ester. Another disadvantage of the process as originallyproposed is that generally as the reaction proceeds the viscosity of thereaction mixture progressively increases until a highly viscous gel-likemass is produced and the surface of the alkali metal becomes coated overand is rendered unreactive.

In order to overcome the above disadvantages, various improvements havebeen proposed from time to time. One such improvement consists in theuse of hydrocarbon solvents. In accordance with this improvement finelydivided alkali metal is suspended in a hydrocarbon and the ester to bereduced, together with the hydrolytic alcohol, are added to the alkalimetal suspension. In order to insure complete reduction of the ester anexcess of both the alcohol and the alkali metal is used. While thisimprovement has resulted in an increase in yield and some increase inreduction eificiency, nevertheless it still permits considerable amountsof gaseous hydrogen to be evolved, which constitutes a waste of alkalimetal. To decrease the amount of alkali metal lo t y hydrogen evolutionit has been proposed to operate the reaction under hydrogen pressure.This method, however, has not resulted in high reduction efiiciencies ona commercial scale.

An object of this invention is to provide an improved method forreducing esters to produce high molecular weight alcohols by reaction ofalkali metal and aliphatic alcohol which will result in high sodiumreduction efliciencies and. high yields of the product. Other objectswill be apparent from the following description of our invention.

We have discovered that the reaction of alkali metal and hydrolyticalcohol on high molecular weight esters may be carried out withsubstantially no side reaction between the hydrolytic alcohol and sodiumto evolve gaseous hydrogen if the ratio between the alcohol and theester added to the reaction mixture is at all times equal to not morethan two moles of hydrolytic alcohol for each mole of ester group to bereduced. For example, if the ester to be reduced is a simple ester of amono-basic, saturated fatty acid, e. g. methyl stearate, two moles ofalcohol 'will be used to one mole of the ester. The correspondingglyceride, e. g. stearin or olein, will require six 5 moles of alcoholper mole of glyceride, since the glyceride molecule contains three estergroups. Our improved process is distinguished from the prior methods inone respect by the fact that whereas prior methods used an excess ofalcohol so that the alcohol functioned both as reactant and as solvent,in our process the alcohol functions only as reactant and does not existin excess. In fact in our process, there is at all times substantially,no free hydrolytic alcohol in the reaction mixture, since the alcoholreacts substantially as fast as it is added to the reaction mixture toform alkali metal alcoholate.

We have further discovered that improved results may be obtained byusing secondary or ter- 40 tiary alcohols as hydrolytic alcohols in theherein described reduction process. The use of these alcohols results inbetter yields of product and more satisfactory operation, as more fullyexplained hereinafter.

In reducing unsaturated fatty acid esters in accordance with ourinvention, we have found that the ethylenic linkages present in suchesters are not reduced to any substantial extent, even when two or moredouble bonds are present, provided 5 there is no conjugate unsaturation.In the case of esters containing conjugated double bonds, only one ofthe double bonds in the conjugate system will be reduced. Therefore, inaccordance with our invention, in addition to two moles of 0 hydrolyticalcohol for each ester group to be reduced, we also add two moles ofhydrolyti'c alcohol (together with at least an equivalent amount ofalkali metal) for each conjugated double bond system (CH:CI-ICH=CH-) inthe ester molecule. If the ester contains only one double bond or aplurality of double bonds not conjugated, we add only two moles of thealcohol per ester group. In any case, the amount of alkali metal usedwill be sufllcient to react with all of the alcohol added; an excess ofalkali metal may be used if desired, without deleteriously affecting theresult as long as the amount of hydrolytic alcohol does not exceed thattheoretically required for the reduction of the ester.

In practicing our invention it is important that the hydrolytic. alcoholand the esters to be reduced be added substantially simultaneously tothe alkali metal and that there be no large excess of either alcohol orester during the operation. If some of the alcohol should be addedbefore adding the ester, or if the alcohol is added in excess of thatrequired to reduce the ester present, the excess alcohol will react withthe alkali metal to evolve hydrogen, even when the alkali metal is notpresent in excess, thus resulting in a waste of the alkali metal. On theotherhand, we have found that if the ester is added to the sodium in theabsence of the hydrolytic alcohol, the ester reacts with the alkalimetal to form certain polymeric compounds (acyloins) which will notthereafter take part in the desired reaction.

In practicing our invention we prefer to use close to the theoreticalamounts of alkali metal (that is, 4 gram atoms per mole of ester groupto be reduced, plus 2 atoms for each conjugated double bond system), orat most only a slight excess, e. g. 1% excess to take care of traces ofwater or other reactive impurities which may be present. As mentionedabove, a substantial excess of alkali metal may be used if desiredwithout deleteriously affecting the reaction, provided that thehydrolytic alcohol is not used in excess. However the use of excessalkali metal ordinarily is of no advantage in practicing our inventionand generally results in a loss of metal because of the difliculty ofrecovering unreacted metal after the reaction has been completed.

It will be apparent that various methods may be used to bring the ester,hydrolytic alcohol and alkali metal into reaction in accordance with ourinvention. We prefer first to form a suspension of finely divided alkalimetal in a hydrocarbon solvent such as xylene and to add to thissuspension with efficient agitation a hydrocarbon solvent solution ofthe ester to be reduced together with the hydrolytic alcohol in theratio of 1 ester equivalent to 2 mols of the hydrolytic alcohol. Thealcohol-ester solution is added slowly with rapid agitation, while thereaction mixture is heated or cooled as required to maintain the desiredreaction temperature.

The temperature of the reaction mixture may vary between wide limits,for example from ordinary room temperatures of around 20-30" up to theboiling point of the solvent. In most cases we have found that the bestyields are obtained by using a reaction temperature above the meltingpoint of the alkali metal, e. g. between and 110 C. when using sodium asthe alkali metal.

After the reaction is complete, a small amount of a lower aliphaticalcohol, e. g. methanol, is added to decompose any traces of unreactedsodium which may be present. Water or acid then is added to decomposethe alcoholates present; we prefer to use a solution of about 9 normalsulfuric acid for this purpose. The acid solution should be addedcautiously with rapid agitation and cooling as necessary. The reactionmixture then is washed with water to remove sulfates and 5 distilled toseparate the reaction product from the solvent. We prefer to distill offthe hydrocarbon solvent at atmospheric pressure and then to distill offthe product in a pure form by vacuum distillation. 10 The followingexamples illustrate specific methods of practicing our invention:

Example 1 Methyl laurate, 535 gms., together with 370 15 gms. oftertiary butyl alcohol were dissolved in 1500 cc. of xylene and slowlyadded during the course of one hour to a suspension of 230 gms. offinely divided sodium in another 1500 cc. of xylene, maintained at atemperature of C. 20 After neutralizing the alkali with sulfuric acidand washing the xylene solution of the higher alcohol with water, thesolvent was removed by distillation and the crude lauryl alcoholproduced was vacuum distilled at 15 mm. pressure. The 25 yield of thecrude lauryl alcohol, was 436 gms. or 92.9% of theory; the yield of purelauryl alcohol was 88.0% of theory.

Example 2 30 Bayberry tallow (containing 6.5% free palmitic acid) 225gms.,-together with 172 gms. of cyclohexanol were dissolved in 700 cc.of xylene and the mixture added in the course of one hour and fortyminutes to a suspension of 79 gms. of finely 35 divided sodium inanother 700 cc. of xylene maintained at a temperature of 100-l05 C. Theproduct, which consisted of cetyl alcohol, mixed with other higheralcohols, was separated and purified as in Example 1. The yield of thepuri- 40 fled product was 81.2% of theory.

Example 3 Beef tallow, 666 gms., along with 346 gms. of secondary butylalcohol were dissolved in I00 cc. of xylene and added in the course of 3hours and 40 minutes to a stirred suspension of 217 gms. 60 of finelydivided sodium in 1000 cc. of xylene at 105-l10 C. The yield of higheralcohols was 90.6% of theory.

Example 5 China-wood oil, 407 gms., and 412 gms. of tertiary butylalcohol were dissolved in 1500 cc. of xylene and the mixture added inabout three hours to a stirred suspension of 256 gms. of finely dividedsodium at 100-ll0 C. The ratio of ester to sodium to hydrolyzing alcoholwas made 70 126:4 instead of 1:4:2, since one of the conjugated doublebonds is reduced along with the eleostearic acid ester group giving analcohol isomeric with linoleyl alcohol. The yield of this alcohol was91.8% of theory. The iodine num- 75 ber ,(Method 01' Ber. 593, 1390-7(1926)) of the China-wood oil was was 230-235. The higher alcoholproduced had an iodine number of 166. The calculated value, assuming theunsaturation to be /3 reduced, would be 165.

Example 6 Spermacetti, 200 gms., together with 65.0 gms. of tertiarybutyl alcohol was dissolved in 700 cc. of toluene and this solution wasadded slowly to a stirred suspension of 40.5 gms. of finely dividedsodium in 700 cc. of toluene at 105 C. The yield of higher alcohols was96.2% of theory.

Example 7 Cocoa butter, 132 gms., together with 43.2 gms.

of absolute ethanol was dissolved in 700 cc. of xylene and the mixtureadded in 45 minutes into a suspension of 43.2 gms. 'of finely dividedsodium in 1000 cc. of xylene. The yield of purified higher alcohols was84.9% of theory. In a similar manner abietic acid esters, wool grease,menhaden oil, cod liver oil, linseed oil and phenyl acetate esters canbe reduced to higher alcohols corresponding to the acids present in theester or glyceride reduced.

In practicing our invention it is important that sufficient of thehydrocarbon solvent is used in proportion to the amount of ester to bereduced, in order to prevent the excessive increase in the viscosity ofthe reaction mixture. The increase in viscosity of the reaction mixtureas the reaction proceeds appears to be due to. the various alkali metalalcoholates which are formed by the reaction. As shown by the equationgiven above, three alkali metal alcoholates may be formed, namely (a)from the hydrolytic alcohol used (b) from the alcohol component of theester and (c) the alcoholate of the higher molecular weight alcoholproduced by reduction of the ester. We have found that alkali metalalcoholates are insoluble or only slightly soluble in hydrocarbonsolvents. In general, the alkali metal alcoholates of the loweralcohols, e. g. ethyl or methyl alcohol, are substantially insoluble inmost hydrocarbon solvents, while those formed from higher alcohols andespecially branched chain higher alcohols have a slight degree ofsolubility which tends to increase in proportion to their molecularweights. In most cases it would be practically impossible to usesuflicient hydrocarbon solvent to dissolve more than a small portion ofthe alcoholates formed by the reaction. If the alcoholate is formed by areaction of alkali metal with the alcohol in the presence of thehydrocarbon solvent, an insoluble precipitate forms which is more orless gelatinous in nature and greatly increases the viscosity of themixture. On the other hand, we have found that when the alcoholates areformed by reacting sodium with the alcohol and the ester insubstantially the theoretical proportions, the alcoholates produced areformed chiefly in the form of colloidal suspensions, that is, in theform of sols rather than gels and hence increase the viscosity to only arelatively small extent. The amount of solvent required in the reductionof a given amount of ester depends therefore on the alcohol component ofthe ester and on the alcohol used as hydrolytic alcohol. For example, wehave found that the formation of sodium methylate in the reactionmixture tends to increase the viscosity of the mixture to a greaterextent than the alcoholates of higher alcohols; hence in general,smaller amounts of solvent are required in the reduction of theglycerides than in the reduction of methyl esters of the high molecularweight acids. As regards the hydrolytic alcohols to be used, as statedabove, those of higher molecular weight form alkali metal alcoholateswhich are somewhat more soluble in hydrocarbon solvents than thoseformed from a lower molecular weight alcohol. The alkali metal compoundsof methanol, for example, are highly insoluble in hydrocarbon solventsand for 10 this reason methanol is not recommended as hydrolyticalcohol. Other alcohols such as ethanol and normal butanol may be usedwith good results, however, providing that the concentration of theester to be reduced is kept sriiiciently low and an excess of hydrolyticalcohol is avoided.

We have discovered that the use of alkali metal alcoholates of secondaryand tertiary alcohols.

i. e. alcohols having two or more carbon atoms attached to the carbonatom to which the hydroxyl group is attached, permits a much greateramount of a given ester to be reduced in a given amount of a hydrocarbonsolvent than the alcoholates of normal alcohols of the same molecularweights. For example, when using either tertiary or secondary butylalcohol as the hydrolytic alcohol in the reduction of the higher fattyacid esters in accordance with our invention and using xylene as asolvent, good results may be obtained with a concentration of 38 gramsof a glyceride per 100 cc. ofsolvent. On the other hand, if ethanol ornormal butyl alcohol is used as the hydrolytic alcohol, theconcentration of the glyceride cannot be more than 10 to 15 grams per100 cc. of solvent; if the concentration is higher than this, thereaction mixture becomes too viscous to permit efficient stirring beforethe reaction is completed.

The employment of the aforementioned secondary and tertiary alcohols inaccordance with our invention is not restricted to the alkali metalreduction processes where the ratio of hydrolytic alcohol to ester islimited as described above. The above enumerated advantages accruingfrom the use of the secondary or tertiary alcohols may be obtained overa wide range of ratio of hydrolytic alcohol to ester. Furthermore, theaddition of secondary or tertiary alcohol to a reaction mixtureemploying a primary alcohol will give improved results, the degree ofimprovement depending chiefly upon the proportion of secondary ortertiary alcohol present.

Various organic liquids, inert to alkali metals and having boilingpoints sufliciently high to allow of their use at the desired reactiontemperatures, may be used as solvents in accordance with our invention.Examples of suitable solvents are aromatic hydrocarbons such as xyleneor toluene and aliphatic hydrocarbons, e. g. petroleum fractions,preferably those high in paraffin hydrocar bons, ethers, e. g. dibutylether, tertiary amines, etc. If the solvent selected contains substancesreactive with alkali metal, an excess of the metal should be used toallow for the consequent sidereactions, or, preferably, the solventshould be purified before use, e. g. by treatment with sodium to removethe reactive constituents.

An important advantage of our novel method resides in the discovery thatit permits reduction of unsaturated esters with little or no reductionof the ethylenic linkages, thereby resulting in the production ofunsaturated higher alcohols, which have useful properties. This isillustrated by Example 3. Heretofore it has not been possible to reducethe unsaturated esters with alcohol and alkali metal without materiallyreducing the double bonds. A further important advantage is thatsubstantially no free hydrogen is evolved, waste of alkali metal andhydrolytic alcohol is avoided, the material cost is decreased and theprocess is consequently more eiflcient than prior methods. A furtheradvantage resides in the employment of secondary and tertiary alcohols,e. g. secondary or tertiary butyl alcohol, as hydrolytic alcohols, whichresults in a more fluid reaction mixture.

Although our method does not require the employment of high pressures'orthe addition of extra reactants such as hydrogen or carbon dioxideduring the reduction reaction, these may be used in practicing ourinvention if desirable. .However, such additional measures ordinarilyare of no advantage in our process.

We claim:

1. A process for the reduction of a higher organic acid comprisingreacting an ester of said acid simultaneously with alkali metal and theapproximately theoretical quantity of a hydrolytic alcohol in a solventmedium substantially inert to alkali metals.

2. A process for the reduction of a higher fatty acid comprisingreacting an ester of said acid simultaneously with alkali metal and theapproximately theoretical quantity of a hydrolytic alcohol in ahydrocarbon solvent medium.

3. A process for the reduction of a higher organic acid comprisingreacting an ester of said acid simultaneously with the approximatelytheoretical quantities of both alkali metal and a hydrolytic alcohol insufilcient hydrocarbon solvent to maintain the reaction in a state offluidity.

4. A process for the reduction of a higher fatty acid comprisingreacting an ester of said acid simultaneously with sodium and theapproximately theoretical quantity of a butyl alcohol in a solventmedium substantially inert to alkali metals.

5. A process for the reduction of a higher fatty acid comprisingreacting a glyceride of said acid simultaneously with the approximatelytheoretical quantities of both sodium and tertiary butyl alcohol insufllcient xylene to maintain the reaction in a state of fluidity.

6. A process for the reduction of a higher fatty acid comprisingreacting a glyceride of said acid simultaneously with the approximatelytheoretical quantities of both sodium and secondary butyl alcohol insufllcient xylene to maintain the reaction in a state of fluidity.

7. A process for the reduction of a higher fatty acid comprisingreacting an ester of said acid simultaneously with alkali metal and ahydrolytic alcohol in a solvent medium substantially inert to alkalimetals, the amount of hydrolytic.alcohol added per mol of ester beingapproximately equal to 2 mols of alcohol for each ester group plus 2mols of alcohol for each conjugated pair of ethylenic linkages in theester molecule and the amount of alkali metal present being-sufficientto react with the alcohol added.

8. A process for the reduction of a higher fatty acid comprisingreacting an ester of said acid simultaneously with sodium and ahydrolytic alcohol in a hydrocarbon solvent, the amount of hydrolyticalcohol added per mol of ester being approximately equal to 2 mols ofalcohol for each ester group plus 2 mols of alcohol for each conjugatedpair of ethylenic linkages in the ester molecule and the amount ofalkali metal present being sumcient to react with the alcohol added.

9. A process for'the reduction of an unsaturated fatty acid comprisingreacting an ester of said acid simultaneously with sodium and a bydrolytic alcohol in a hydrocarbon solvent, the amount of hydrolyticalcohol added per mol of 5 ester being aproximately equal to 2 mols ofalcohol for each ester group plus 2 mols of alcohol for each conjugatedpair of ethylenic linkages in the ester molecule and the amount ofalkali metal present being sumcient to react with the alcohol added- 10.A process for the reduction of higher fatty acids comprising dissolvingan ester of a higher fatty acid and a hydrolytic alcohol in the ratio ofapproximately 2 mols of alcohol to one moi of the ester in a hydrocarbonsolvent and reacting the solution with a suspension of alkali metal in asolvent inert to alkali metals.

11. A process for the reduction of higher fatty acids comprisingdissolving a glyceride of a higher fatty acid and a hydrolytic alcoholin the ratio of approximately 6 mols of alcohol to one mol of theglyceride in a hydrocarbon solvent, the atmospheric boiling point ofwhich is not lower than about 100 C. and reacting the solution with asuspension of sodium in an organic liquid containing approximately 12atoms of alkali metal per mol of said glyceride at a temperature abovethe melting point of the alkali metal.

12. A process for the reduction of higher fatty acids comprisingdissolving an ester of a higher fatty acid and a butyl alcohol in theratio of approximately two mols of the alcohol to one mol of the esterin xylene and reacting the solution with'approximately four gram-atomsof sodium per gram-moi of said ester suspended in a liquid hydrocarbonhaving a boiling point above 100 C., at a temperature above the meltingpoint of sodium.

13. A process for the reduction of higher fatty4o acids comprisingdissolving a glyceride of a higher fatty acid and tertiary butyl alcoholin the ratio of approximately 6 mols of the alcohol to one mol of theglyceride in xylene and reacting the solution with a hydrocarbonsuspension of sodium containing approximately 12 gramatoms of sodium pergram-moi of said glyceride at a temperature of 100 to 110 C.

14. A process for the reduction of higher fatty acids comprisingdissolving a glyceride of a higher fatty acid and secondary butylalcohol in the ratio of approximately 6 mols of the alcohol to one molof the glyceride in xylene and reacting the solution with a hydrocarbonsuspension of sodium containing approximately 12 gram-atoms of sodiumper gram-moi of said glyceride at a temperature of 100 to 110 C.

15. A process for the reduction of a higher fatty acid comprisingreacting an ester of said acid simultaneously with alkali metal and analcohol having at least two carbon atoms attached to the carbinol group.

16. A process for the reduction of a higher fatty. acid comprisingreacting an ester of said acid simultaneously with alkali metal and theapproximately theoretical amount of an alcohol having at least twocarbon atoms attached to the carbinol group in a solvent medium substantially inert to alkali metals.

17. A process for the reduction of a higher fatty acid comprisingreacting an ester of said acid simultaneously with alkali metal andtertiary butyl alcohol.

18. A process for the reduction of a higher fatty acid comprisingreacting an ester of said acid simultaneously with alkali metal and analcohol having at least two carbon atoms attached to the carbine! groupin a hydrocarbon 5 solvent medium.

19. A process for the reduction of a higher fatty acid comprisingreacting an ester of said acid simultaneously with alkali metal andtertiary butyl alcohol in a hydrocarbon solvent medium.

NORMAN D. SCO'I'I. VIRGIL L. HANSLEY.

